The present invention relates generally to hand-holdable electronic calculating devices.
Battery-powered, hand-holdable electronic calculating devices (or "calculators") are well-known for rapidly performing calculations ranging from relatively easy arithmetical operations to complex mathematical computations. The simplest in design of these calculators features a display, a keyboard with individual input keys for the digits 0-9, functional keys for the arithemetic operations of addition, subtraction, multiplication and division, an "equal" key, and of course the appropriate electronic circuitry to functionally implement each of these features. Additional features of still relatively simple calculators include an input key for a decimal point, keys for clearing the results of previous calculations stored in the device or for clearing only the last number entry, an auxiliary memory for storing and recalling intermediate calculations, a constant function allowing entry and storage of a fixed number to be used over and over again in addition, subtraction, multiplication or division, and a percent key by which an entry can be used more readily to take a percentage of a number. Beyond this, a wide variety of relatively complex and expensive scientific, business and programmable calculators are available.
Despite the low cost and ready availability of the aforedescribed simple calculators, many, if not most, persons heretofore have not taken advantage of them to the fullest possible extent. In particular, it has been noted that shoppers typically have not used electronic calculators to keep track of their purchases while selecting large numbers of items during grocery shopping. This is despite limited budgets of shoppers, recent high rates of inflation, the risk of errors by checkers in checking-out shoppers' selections and the difficulty of catching those errors, and concerns for the accuracy and reliability of semi-automatic check-out by means of scanners that optically read specially encoded portions of the labels on items to determine the price to be charged to the shopper.
A major reason that most shoppers do not take advantage of electronic calculators is believed to be that they consider even the simplest calculators to be overly-complex and inconvenient to use. For example, a common characteristic of all electronic calculators is that a "plus" key or an "equal" key must be pressed after each number entry is made in order to add the numbers. The proper sequence for pressing these keys can differ among various calculators. An inexperienced operator can very easily become confused, pressing one of these keys more than once, and possibly produce an erroneous total. Those familiar with the design of calculators will recognize other errors novice or occasional operators are prone to make.
Thus, despite the relative simplicity of the most basic electronic calculators, there is a need for improvement in the foregoing and in other respects. The present invention is directed to these ends.